Dictionaries of synonyms (thesaurus dictionaries) are useful for search processing or processing of transforming search words inputted for searching. For example, new products or services are provided one after another on Internet, and new words are created. The thesaurus dictionaries also need to support these new words. For example, Patent Document 1 discloses a dictionary generating device which learns an association between words based on a frequency table obtained by integrating a co-occurrence frequency table of words in a predetermined range in document and a thesaurus frequency table obtained by transforming thesaurus information into a virtual frequency table, and creates a conceptual dictionary by compressing the integrated frequency table.